My above-cited copending patent application describes a system wherein a yarn package is carried on a spindle rotated at high speed about its longitudinal axis. A tube concentric with the axis has an open end and forms a cup completely spacedly surrounding the yarn package with its rim lying axially beyond the end of the yarn package. A takeup eye or guide is provided adjacent this end of the assembly but is spaced from the end of the tube, and generally centered on the rotation axis of the tube and the yarn package. Thus the yarn is pulled off the yarn package to form a balloon which extends axially beyond the end of the bobin up to the takeup eye. In this manner there is formed within the tube a body of air which rotates with the yarn package, and above the tube between it and the takeup guide there is formed a vortex having rotation speed which decreases away from the yarn package. Pulling the yarn through this vortex breakes it effectively and therefore tensions the yarn to an extent which is determined by the distance between the guide and the upper rim of the tube, this business determining the position of the yarn in the vortex. The yarn package lies below the rim of the tube or shell so that initially the yarn is drawn off through a body of air rotating the bobin and the shell, and is thereafter drawn through an air vortex with axially decreasing air velocity.
Such twisting devices are usually arranged upright, rotatable about vertical axes and in groups on a common horizontally elongated frame. In order to allow servicing of each of these twisting arrangements they are arranged in a straight line spaced apart by a distance sufficient to allow the operators to load new yarn packages into them and remove the old core.